1. Field of the Invention
This invention relates to the field of ventilator hoods for removing airborne grease and smoke from spaces above cooking appliances, particularly in the kitchens of catering businesses and restaurants.
2. Description of the Prior Art
An earlier development of an apparatus for removing fumes from a space above a cooking appliance has been described in U.S. Pat. No. 3,943,836, issued Mar. 16, 1976, wherein there is described a vortex-type smoke ventilator wherein the incoming supply of air is caused to swirl and mix with uprising fumes before being exited through filters into an exhaust duct. However, this apparatus had certain disadvantages in that the swirling air developed under the hood did not have sufficient velocity to break down large grease particles on its way to be passed through a filter, thus causing the larger globules of grease to adhere to the surface of the filter, eventually causing a grease film to develop over the entire surface of the filter. When a globule of grease is captured by the swirling air, it is bound to be diminished in size before it approaches the filter to pass through it and exit through the exhaust duct.
The faster the air flows in a vortex below the hood, the more effective is the centrifugal grease-separation action in the apparatus.
Another disadvantage of the known apparatus was the lack of control exerted over the supplied air passing through the hood volume, so that all of the supplied air entering the hood volume would depart through the filters downwards through the exhaust duct. Too much supplied air would cause some of the supplied air to leave the hood volume and enter into the interior of the kitchen carrying some of the fumes with the supplied air. The best procedure is to have almost all of the supplied air enter the hood volume and mix with the fumes and depart through the filters into the exhaust duct. On the other hand, if too much supplied air is exhausted through the exhaust duct, some of the heat in the kitchen area will be drawn and pass through the exhaust duct. In a general arrangement, the apparatus is about 10 feet long and incorporates three cooking sections. For example, starting from the left side, there is a workspace, followed by a broiler, followed by another workspace, followed by a fryer, followed by a workspace, and terminating in a range top. To improve the flow of air flowing over the spaces occupied by the broiler, the fryer, and the range top, it is desirable to provide compensator air plates adjacent the cooking areas, the compensator plates being provided with a multiple number of openings which are adapted to be reduced in size with another overlapping compensator plate to adjust the flow of air above the broiler, the fryer, and range top areas. To improve the grease-collecting features of a bank of abutting filters, the filters should not be coupled by coupling members, which reduce the filtering area, thereby permitting all of the air to flow through and permit particulate matter to be trapped by the filters. Also, the efficiency of the hood is increased because the uniformity of the baffle spacing of the full length of the filter bank achieves uniform laminar flow, whereas the conventional filter arrangement has unequal side margins, and filler panels are necessary. These filler panels deflect the incoming supplied air downward, thereby reducing the air volume capacity of the hood. In the earlier apparatus, an upwardly extending exhaust plenum would extend across the full length of the hood and slope upwardly and inwardly until the reduced opening at the top of the plenum would connect with a duct leading to an exhaust fan. To simplify the construction of the apparatus, a horizontally extended exhaust plenum interconnects with an exhaust air duct. Therefore, this arrangement saves considerable time in preparing the apparatus, and at the same time, saving in time and material construction. An equalizer vane member is used in conjunction with the horizontally extended exhaust plenum and replaces the former bulky and extensive exhaust plenum. The equalizer vane member achieves the same results as the upwardly extending exhaust plenum by restricting the exhaust air flow more at the center one-third duct penetration section than the left and right one-third sections. This design, which is modular for all lengths of hoods, achieves uniform laminar exhaust air flow the full length of the filter bank. This design feature contributes to the success of the hood by simplifying fabrication and installation.